Been a long time member, but hardly ever post. First off this site is awesome, I have learned so much from here. Did my own Birf repack awhile , there is no way it would have been as successful without the posts on here. I do have the FSM, which is mandatory as well for wrenching on it IMHO. Rig is a '96.
A quick history on my P0401. CEL came on a few years ago, and I started reading up on it. Bought a new EGR modulator (without even testing the old one, stupid me), still threw the code. It was the wife's daily driver so I did not dig any deeper at the time. Finally started to dig into it a month or so ago. I tested the VSV, it was bad, installed a new one. While in there I cleaned up the throttle body, and all the small vacuum passages into it. I checked the EGR port through the intake, it was clear. Still throwing the code.
So then I went to test the EGR valve by applying vacuum to it while idling, and it had no effect, it kept idling perfectly. So I thought that was the issue. Bought a new EGR valve, still throwing the code! I tested the new EGR by putting vacuum to it at idle, and it still idles perfectly. With engine off I can apply vacuum to the EGR and I hear the diaphram moving so I'm pretty sure the valve is OK. By the way I did check the passage through the intake again by removing the EGR temp sensor, and it almost stalled right away, so I'm getting plenty of vacuum through there.
I checked the EGR temp sensor while I had it off, and it appears to check out OK. I did not do the "oil bath" test to make sure the resistance changes with the temp, I suppose I should try that. But the inability to make the engine stumble when applying vacuum to the EGR port has me stumped. There is a lot about that test to make sure that the engine stumbles, but I can't seem to find out what to look for if that test fails. It would seem to me that the test opens the EGR when it is not supposed to (at idle) and allows exhaust gas into the intake, which essentially dumps exhaust gas into the intake which makes the engine stumble, correct? So by that not happening, I am not dumping the exhaust gas in, right? Looks like I should pull the EGR and see if the pipe coming from the exhaust to the EGR is plugged somehow. That seems unlikely, but I don't know what else to try at this point. Any other ideas? I'm getting close to buying the radio shack resistor. But thinking of selling the rig (sadly) and don't want to do that to the next owner, in case they have to get it through emissions.
Any help is appreciated.
Thanks,
Kevin
A quick history on my P0401. CEL came on a few years ago, and I started reading up on it. Bought a new EGR modulator (without even testing the old one, stupid me), still threw the code. It was the wife's daily driver so I did not dig any deeper at the time. Finally started to dig into it a month or so ago. I tested the VSV, it was bad, installed a new one. While in there I cleaned up the throttle body, and all the small vacuum passages into it. I checked the EGR port through the intake, it was clear. Still throwing the code.
So then I went to test the EGR valve by applying vacuum to it while idling, and it had no effect, it kept idling perfectly. So I thought that was the issue. Bought a new EGR valve, still throwing the code! I tested the new EGR by putting vacuum to it at idle, and it still idles perfectly. With engine off I can apply vacuum to the EGR and I hear the diaphram moving so I'm pretty sure the valve is OK. By the way I did check the passage through the intake again by removing the EGR temp sensor, and it almost stalled right away, so I'm getting plenty of vacuum through there.
I checked the EGR temp sensor while I had it off, and it appears to check out OK. I did not do the "oil bath" test to make sure the resistance changes with the temp, I suppose I should try that. But the inability to make the engine stumble when applying vacuum to the EGR port has me stumped. There is a lot about that test to make sure that the engine stumbles, but I can't seem to find out what to look for if that test fails. It would seem to me that the test opens the EGR when it is not supposed to (at idle) and allows exhaust gas into the intake, which essentially dumps exhaust gas into the intake which makes the engine stumble, correct? So by that not happening, I am not dumping the exhaust gas in, right? Looks like I should pull the EGR and see if the pipe coming from the exhaust to the EGR is plugged somehow. That seems unlikely, but I don't know what else to try at this point. Any other ideas? I'm getting close to buying the radio shack resistor. But thinking of selling the rig (sadly) and don't want to do that to the next owner, in case they have to get it through emissions.
Any help is appreciated.
Thanks,
Kevin
